The invention relates to a method for orchestrating of services of a service-oriented automation system, with system components offering services representing their functionality and services querying other system components, with the behavior of the automation system being governed by orchestration of the services of the system components by means of at least one orchestration machine and to an orchestration machine for orchestrating of services of a service-oriented automation system, comprising system components like intelligent mechatronic components, control components and/or decision components (DSC), each of which provides a set to services which represents their internal functionalities and is queried by other system components.
One method for orchestration of a service-oriented automation system and an orchestration machine is described in an article by F. Jammes, H. Smith et al.: “Orchestration of service-oriented manufacturing processes,” IEEE 2005, vol. 1, pages 617 to 624. A typical feature of a service-oriented automation system is that various processes are compiled and executed to form a complex process of higher order. This pattern is repeated at various levels, namely composition of field devices for formation of machines, compositions of machines for formation of work cells and work paths, composition of machine-level processes for formation of fabrication systems and plants. As soon as the process is compiled as a complete ecosystem of services, it is desirable that the complexity linked with the coordination of atomic services assigned to the processes is encapsulated in a single service interface.
The practice of sequential and synchronized execution of services related to a closed business or fabrication process is called orchestration in the technical vocabulary. An orchestration machine implements the application logic that is necessary to orchestrate atomic services and proves a high-level interface for the combined services (processes).
The combining and orchestrating of web services has attained especial significance in recent times. In this connection, a goal is pursued of forming complex processes by combination of web services that are applicable via multiple hierarchical levels.
To provide flexibility, it is recommended that a web services orchestration description (model-based orchestration) be used, which describes the operational sequences of the modeled system. These orchestration descriptions can be interpreted in real time by machines which interpret the operational sequence in real time, to avoid the use of ad-hoc, hard-coded implementations.
At present, principally two specifications for orchestration of web services are known, one being the Business Process Management Language (BPML), the other the Process Specification Language (PSL), especially for representation of fabrication processes.
In industry, however, the Business Process Execution Language for Web Services (BPEL4WS) has often been used, which is also known under the abbreviations WS-BPEL or BPEL.
However, one disadvantage of orchestration machines obtainable currently is that they are designed for enterprise-level systems. These implementations run on top of an application server and occupy storage areas around 10 MB. For service coordination at the device level, the orchestration machine must in fact run in an embedded device with limited resources.